In many applications of working or disintegrating technology, tools are used, which have been hard-faced with diamond grains in order to improve the abrasive properties. For example, hollow drilling crowns, which are equipped at their front end with cutting segments, are used for producing boreholes or break-throughs of larger diameters. Wall saws and cutting-off wheels for cutting concrete, stone or ceramic are also hard-faced at their periphery with cutting segments. The cutting segments consist essentially of single diamond crystals, which are embedded in a metallic matrix. The grain size of the single diamond crystals, used for such cutting segments, is about 300 .mu.m to about 600 .mu.m. The single diamond crystals are not only disposed at the surface of the cutting segments, but are also distributed relatively uniformly over a portion of the height of the cutting segments. During the processing of the substrate, the edges of the single diamond crystals, protruding out of the surface of the matrix material, engage the material that is to be removed. If the single diamond crystals at the surface are lost, the matrix materials is worn away until new edges of single diamond crystals below are exposed.
In use, the edges can gradually become rounded or the single diamond crystals can break or fall completely out of the matrix material. Because of the relatively large grain size of the single diamond crystals, the number of effective cutting edges for the abrasive processing of the substrate is relatively small. If therefore a single diamond crystal drops out because of rounded edges or breakage or because it falls out of the matrix material, the cutting effectiveness of the cutting segments is impaired until the missing cutting edge is replaced once again by the exposure of a new single diamond crystal. This also has a disadvantageous effect on the achievable cutting speed of the cutting segment.
U.S. Pat. No. 4,591,364 discloses the use of diamond cutting bodies, which are agglomerated from diamond grains of a smaller grain size of typically about 70 .mu.m to about 125 .mu.m and predominantly a metallic binder material, for coating grinding disks. The mixture of diamond grains and binder material is sintered together in a sintering process to a 2-dimensional sinter cake. The 2-dimensional sinter cake is then broken up into small particles and screened. The screen fraction with an agglomerated grain size of about 149 .mu.m to about 250 .mu.m is used to coat the grinding disks. The breaking up of the sinter cake leads to a relatively large particle size distribution of the agglomerated composite cutting bodies, so that a not inconsiderable proportion of the agglomerates is either too large or too small for coating the grinding disks. Not only is the particle size of the rejected fractions quite different; due to the process of breaking the sinter cake, the geometric shape of the rejected fractions is also quite different There is also the danger that the fractions are damaged mechanically by the process of breaking. Therefore, at best, the rejected grain size fractions are ground further in order to be able to use them finally as grinding or polishing agents.